1. Field of the Invention
The present invention relates to a conductive sintered oxide which has electrically conductive properties and which changes in resistivity with a change in temperature. The invention further relates to a thermistor element including the sintered oxide, and to a temperature sensor including the thermistor element.
2. Description of the Related Art
Applications of thermistor elements and temperature sensors include measurement of exhaust gas temperature from internal-combustion engines such as automobile engines. For use in these applications, temperature sensors are desired not only for temperature measurements in high-temperature regions, but also for detecting low temperatures so that a failure (breakage of wire) of the temperature sensor can be detected with, for example, OBD systems (on-board diagnostic systems) or the like.
Patent document 1 discloses, as a technique for satisfying this need, a conductive sintered oxide which has a temperature gradient constant (constant B) of about 2,000-3,000K.
[Patent Document 1] JP-A-2007-246381
3. Problems to be Solved by the Invention
However, the temperature range to be measured by thermistor elements vary, and there is a need for a thermistor element that has an even lower value of constant B, for example, a constant B of 2,000K or lower, which makes the thermistor element useful over a wider temperature range.
Such a thermistor element is suitably used for temperature measurements in the range of −40° to +600° C., for example, in exhaust gas temperature measurements such as the application described above. In addition, with respect to detection of a failure in a temperature sensor employing such a thermistor element, detection of wire breakage in a lower-temperature region and detection of short-circuiting in a higher-temperature region can be precisely made based on the output of the temperature sensor (thermistor element).
Furthermore, there is a need for such a thermistor element which has stable properties and does not change in resistance with the lapse of time even when exposed to high temperatures (e.g., +600° C.).